Light emitting device

ABSTRACT

A light-emitting device including a substrate with a top surface and a bottom surface opposite to the top surface and a plurality of LED chips disposed on the top surface and configured to generate a top light visible above the top surface and a bottom light visible beneath the bottom surface, each LED chip comprising a plurality of light-emitting surfaces. The substrate has a thickness greater than 200 μm and comprises aluminum oxide, sapphire, glass, plastic, or rubber. The plurality of LED chips has an incident light with a wavelength of 420-470 nm. The top light and the bottom light have a color temperature difference of not greater than 1500K.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of co-pending application Ser. No.16/365,115 filed on Mar. 26, 2019, which is a Continuation ofapplication Ser. No. 15/663,125 which issued as U.S. Pat. No. 10,247,395on Apr. 2, 2019, which is a Continuation of application Ser. No.14/886,787 which issued as U.S. Pat. No. 9,741,699 on Aug. 22, 2017,which is a continuation of application Ser. No. 13/834,246 which issuedas U.S. Pat. No. 9,166,116 on Oct. 20, 2015; and this application claimspriority of Application No. 101119098 filed in Taiwan on May 29, 2012,Application No. 101121921 filed in Taiwan on Jun. 19, 2012, ApplicationNo. 101131198 filed in Taiwan on Aug. 28, 2012, Application No.101131643 filed in Taiwan on Aug. 30, 2012, Application No. 101125599filed in Taiwan on Jul. 16, 2012, Application No. 101132187 filed inTaiwan on Sep. 4, 2012, and Application No. 101132185 filed in Taiwan onSep. 4, 2012 under 35 U.S.C. § 119; the entire contents of all of whichare hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a light emitting device comprisingsemiconductor light emitting diode (LED) chips, and particularly to alight emitting device comprising at least one LED chip which emits lightomni-directionally, and a light emitting apparatus using same.

BACKGROUND OF THE INVENTION

In the field of lighting technology, the development trends for lightsources are low cost, environmental friendliness, and power saving inorder to acquire better lighting performance under the condition ofconsuming less power. These trends make LEDs play an important role inthe development.

Practically, there are still limitations and challenges for applyingLEDs or similar light emitting units to lamps for lighting. In the past,using LEDs as a light source called for depositing multiple LED chips ona plane and further providing an optical reflection mechanism to guideor broadcast the light emitted from the LED chips emitting lightdirectionally in the beginning.

This kind of arrangement described above was not appropriate tosubstitute for traditional lamps with wide lighting angles. Because onlya portion of light generated by the LED chips propagated in thedirection of lighting while the other portions were absorbed or lostduring the reflection processes, the lighting efficiency was low and thenumber of the LED chips must be increased for compensation and meetingthe brightness requirement for lighting. Therefore the cost of thetradition LED lamp was high and the benefit for saving energy wasinsufficient.

Moreover, in traditional LED lamps, the substrates on which LED chipswere deposited were planar, firm, and opaque. Thereby, the flexibilityof disposing LED chips was limited. For example, when the substrateswere non-planar, the light generated by the LED chips deposited on thesubstrates would be shielded or blocked accordingly, which wasunfavorable for reducing power consumption and costs of traditional LEDlamps.

SUMMARY

An objective of the present invention is to provide a light emittingdevice with high reliability, high lighting efficiency, and low cost.

Another objective of the present invention is to provide a lightemitting apparatus comprising multiple light emitting devices arrangedsymmetrically or asymmetrically for enhancing the light intensity of thelight emitting apparatus. Meanwhile, the lighting uniformity for variousdirections can be maintained and the required light shapes can beprovided.

Still another objective of the present invention is to provide a lightemitting apparatus comprising a lamp housing for applying to lamps,signboards or backlight units.

Accordingly, for achieving the objectives described above, the presentinvention discloses a light emitting device comprising a transparentsubstrate which light can pass through and at least one LED chipcomprising multiple light emitting surfaces and emitting lightomni-directionally. Wherein the substrate has a support surface on whichthe LED chip is disposed, and one of the light emitting surfaces of theLED chip and the support surface form an illuminant first main surface.Because the light emitting angle of the LED chip is wider than 180°, thelight emitted by the LED chip will penetrate into the substrate and atleast partially emerge from a second main surface corresponding to thefirst main surface of the substrate. According to the present invention,the light emitting device using LED chips can provide sufficientlighting intensity and uniform lighting performance. Additionally, thenumber and the arrangement of the substrates of the present inventioncan be modified for adjusting brightness, so the light emitting devicehas more flexibility for various applications.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A˜1B show structural schematic diagrams of the light emittingdevice according to the embodiments of the present invention;

FIGS. 2A˜2C show schematic diagrams of the light emitting devicecomprising the LED chip in various forms coupled to the conductorsaccording to the embodiments of the present invention;

FIGS. 3A˜3B show schematic diagrams of the light emitting devicecomprising the wavelength conversion layer according to the embodimentsof the present invention;

FIG. 4 shows a schematic diagram of the light emitting apparatuscomprising the support base according to one embodiment of the presentinvention;

FIGS. 5A˜5D show top views of the arrangement of the light emittingdevice deposited on the support mechanism of the light emittingapparatus point- or line-symmetrically according to the embodiments ofthe present invention;

FIG. 6 shows a schematic diagram of the light emitting device comprisingthe LED chips with light emitting surfaces according to one embodimentof the present invention;

FIG. 7 shows a schematic diagram of the light emitting apparatuscomprising the circuit board according to one embodiment of the presentinvention;

FIGS. 8A˜8B show schematic diagrams of the light emitting apparatuscomprising the lamp housing according to the embodiments of the presentinvention;

FIG. 9 shows a cross-sectional view of the light emitting apparatus forapplication according to one embodiment of the present invention;

FIG. 10 shows a schematic diagram of the light emitting apparatuscomprising the reflector according to one embodiment of the presentinvention;

FIG. 11 shows a schematic diagram of the light emitting apparatuscomprising diamond-like carbon film according to one embodiment of thepresent invention;

FIGS. 12A˜12C show schematic diagrams of the light emitting apparatusaccording to the embodiments of the present invention;

FIGS. 13A˜13B show schematic diagrams of the light emitting apparatusaccording to the embodiments of the present invention; and

FIGS. 14A˜14D show schematic diagrams of the light emitting apparatusfor various applications according to the embodiments of the presentinvention.

DETAILED DESCRIPTION

As shown in FIGS. 1A and 1B, the first embodiment of the presentinvention discloses a light emitting device 1 comprising a transparentsubstrate 2 which light can pass through, a support surface 210, a firstmain surface 21, a second main surface 22, and at least one LED chip 3emitting light omni-directionally.

Wherein the number of the LED chips 3 deposited on the support surface210 of the sheet-shaped substrate 2 according to the embodiment is 9,and the embodiment arranges the LED chips 3 as a 3×3 matrix. The LEDchip 3 comprises multiple light emitting surfaces, and one of the lightemitting surfaces 34 and the support surface 210 form the illuminantfirst main surface 21 of the light emitting device 1. Because the lightemitting angle of the LED chip 3 is wider than 180°, at least a portionof light emitted from the LED chip 3 will penetrate into the substrate 2from the support surface 210 and pass through the substrate 2. Then theincident light in the substrate 2 will at least partially emerge fromthe second main surface 22 and/or the first main surface 21 of the lightemitting device 1.

The material of the substrate 2 can be aluminum oxide, sapphirecontaining aluminum oxide, glass, plastics, or rubber. According to apreferred embodiment of the present invention, a sapphire substrate isadopted for its essentially single crystal structure and better lighttransmissivity. In addition, it has superior capability in heatdissipation, which can extend the lifetime of the light emitting device1. However, traditional sapphire substrates have the problem of crackingwhen being assembled with other units of the light emitting apparatus.In order to solve this reliability problem, the thickness of thesubstrate 2 of the present invention should be greater than or equal to200 μm as verified by experiments for practical applications.

Moreover, according to the present invention, the difference betweencolor temperatures of the light emerging from the first main surface 21and the light emerging from the second main surface 22 is set equal toor smaller than 1500K by adjusting the parameters of the substrate 2,thickness or composition for example, or phosphor deposited thereon.Therefore, the light emitting device 1 of the present invention has anoverall consistent lighting performance. According to another embodimentof the present invention, the light transmissivity of the substrate 2 isset greater than or equal to 70% when the range of the wavelength of theincident light is 420˜470 nm with the thickness of the substrate 2 beingthe value described above.

As shown in FIGS. 2A˜2C, there are further embodiments of the presentinvention. For acquiring power for emitting light, an LED chip 3 of alight emitting device according to the present invention includes afirst electrode 31 and a second electrode 32 coupled electrically with afirst conductor 23 and a second conductor 24 located on the substrate 2respectively. More particularly, FIG. 2A shows a lateral type LED chip 3deposited on the substrate 2 and coupled with the conductors 23, 24 bywire bonding; FIG. 2B shows a flip-chip type LED chip 3 deposited on thesubstrate 2 and coupled with the conductors 23, 24 by chip bondingwherein the conductors are circuit patterns on the substrate 2. FIG. 2Cshows an LED chip 3 having the electrodes 31, 32 disposed on both sidesof the epitaxial layers 33 respectively, and the LED chip 3 isvertically deposited on the substrate 2 with the edges of the electrodes31, 32 connected to the conductors 23, 24.

As shown in FIGS. 3A˜3B, there are further embodiments of the presentinvention. A light emitting device 1 according to the present inventionfurther includes a wavelength conversion layer 4, which is disposed on afirst main surface 21 or/and a second main surface 22 of the lightemitting device 1. Alternatively, the wavelength conversion layer 4 canbe disposed on an LED chip 3 directly (not shown in the figures).According to the embodiments of the present invention as shown in thefigures, the wavelength conversion layers 4 including at least one kindof fluorescent powder receive at least a portion of light emitted fromthe main surfaces 21, 22 and convert to the light with differentwavelength. According to one embodiment shown in FIG. 3A, one of thewavelength conversion layers 4 encapsulates and contacts the LED chip 3directly. According to another embodiment shown in FIG. 3B, one of thewavelength conversion layers 4 covers the LED chip 3 and forms a spacebetween the wavelength conversion layer 4 and the substrate 2 forreceiving/converting at least a portion of the light emitted by the LEDchip 3 to the light with different wavelength. For example, when the LEDchip 3 emits blue light the wavelength conversion layer 4 converts aportion of the blue light to yellow light. Then the light emittingdevice 1 will eventually emit white light by mixing the blue light andthe yellow light. Additionally, the space can be filled with othermaterials like epoxy, air, phosphor, etc., according to various opticsand reliability requirements.

The intensity of the light from the first main surface 21 is slightlydifferent from the intensity of the light from the second main surface22. In addition, as described earlier, the further embodiment of thepresent invention is to set the difference in color temperatures of theemerging light equal to or smaller than 1500K. Additionally, accordingto a preferred embodiment of the present invention, the ratio of thequantity of the fluorescent powder in the wavelength conversion layer 4on the first main surface 21 to that on the second main surface 22 is1:0.5 to 1:3, or other values in order to improve the wavelengthconversion efficiency and the light emitting performance of the lightemitting device 1.

As shown in FIG. 4, a light emitting apparatus of the present inventioncomprises a light emitting device 1 as described in the previousembodiments and a support base 5. Wherein the substrate 2 couples to thesupport base 5 for forming a light emitting apparatus 11, and there is afirst angle θ₁ between the substrate 2 and the support base 5. The firstangle θ₁ is adjustable according to the required light shape of thelight emitting apparatus. According to a preferred embodiment, the firstangle θ₁ ranges from 30° to 150°.

As shown in FIGS. 5A ^(˜) 5D, a light emitting apparatus 11 according tofurther embodiments of the present invention further comprises multiplelight emitting devices 1 for enhancing the brightness and meetingdifferent light shape requirements. Users can dispose the light emittingdevices 1 comprising a plurality of substrates 2 on a support mechanism50 such as the support base 5 at the same time. The arrangement can besymmetrical or asymmetrical. The support base 5 or the support mechanism50 has a virtual center axis C. The preferred arrangement is to disposethe multiple substrates 2 point-symmetrically or line-symmetricallyrelative to the virtual center axis C on the support mechanism 50, sothat the light emission of the overall light emitting apparatus 11 canbe uniform. (The LED chips 3 are omitted in the figures.) Particularly,the shape of the support mechanism 50 can be a polygon, square,rectangle or regular hexagon for example, or circle or even a hollowcircle or a hollow polygon for various applications. According toanother embodiment, at least a portion of multiple light emittingdevices 1 is disposed concentratively or dispersively in an asymmetricalmanner for meeting the requirement for the light shapes of the lightemitting apparatus 11 in various applications (not shown in thefigures).

In the present invention, the support base 5 or the support mechanism 50can be a multi-functional base for supporting, supplying power,connecting, and dissipating heat simultaneously. The support bases 5 orthe support mechanism 50 can comprise such materials as metal, ceramic,glass, plastics, resin or PCB (printed circuit board), just like thebase or the socket of a traditional commercial bulb. According to apreferred embodiment, the support base 5 or the support mechanism 50comprise a flexible metal compound. As shown in FIG. 6, one of the lightemitting surfaces 34 of the LED chip 3 is the exposed surface in thestructure essentially parallel to the support surface 210 of thesubstrate 2. According to one of the preferred embodiments of thepresent invention, the area of the first main surface 21 or the secondmain surface 22 shall be at least five times the total area of theplurality of light emitting surfaces 34 or the single area of the lightemitting surface 34. Then there will be preferred area utilization rate,light emitting and heat dissipation efficiencies of the light emittingdevice 1.

As shown in FIG. 7, the light emitting apparatus 11 of the presentinvention can further comprise a circuit board 6 on the support base 5for coupling with an internal or external power supply. The circuitboard 6 couples to the first and second conductors 23, 24 on thesubstrate 2 (not shown in the figure) for connecting electrically withthe LED chips 3 and supplying the power required for emitting light. Thecircuit board 6 can also be integrated with the support base 5,therefore the LED chips 3 can be connected electrically with the supportbase 5 through the first and second conductors 23, 24 (not shown in thefigure). Thereby, power can be directly provided to the LED chips 3 viathe support base 5.

As shown in FIGS. 8A-9 and 14A-14D, in order to prevent pollution,corrosion, or wear on the substrate 2 and the LED chips 3 from ambientparticles such as dust and moisture, the light emitting apparatusaccording to further embodiments of the present invention furthercomprises a lamp housing 7. The lamp housing 7 couples to the supportbase 5 or the support mechanism 50 and at least partially covers thesubstrate 2, wherein the form of the lamp housing 7 can be a tube, abulb, or a box. Furthermore, the wavelength conversion layer 4 describedabove can be disposed optionally on the lamp housing 7.

FIG. 8A shows a schematic diagram of a light emitting apparatus 11according to an embodiment of the present invention. The light emittingapparatus 11 here is a tube, wherein the lamp housing 7 is a transparenttubular structure. Then the light emitting device 1 and the supportmechanism 50 are disposed therein. In FIG. 8A, a single light emittingdevice 1 is disposed therein. As shown in FIG. 8B, when two or morelight emitting devices 1 are disposed in the lamp housing 7, the firstmain surfaces 21 of the plurality of light emitting devices 1 can bearranged as mutually unparallel. In addition, at least a portion of thelight emitting device 1 is disposed in the room formed by the lamphousing 7 and not tightly close to the inner walls of the lamp housing7. According to a preferred embodiment, there is a distance D greaterthan 500 μm between the light emitting device 1 and the lamp housing 7.The lamp housing 7 can also be formed by molding, making the lightemitting device 1 at least partially sealed and directly contacted bythe lamp housing 7.

According to another embodiment of the present invention, the lightemitting apparatus 11 is a light box as shown in FIG. 9. The lamphousing 7, which is used as a signboard in this case, has at least onesurface 71 mainly used for printing advertisements. Then the lightprovided by the first and second main surfaces 21, 22 of the lightemitting device 1 according to the present invention form the backlightfor the surface 71. The light emitting devices 1 can further be inclinedor rotatable with a second angle θ₂ relative to the surface 71, whereinthe second angle θ₂ is set between 0° to 45°. (In this case shown inFIG. 9, θ₂ is 0° and hence not shown.) According to a preferredembodiment, there is a distance D greater than 500 μm between the lightemitting device 1 and the lamp housing 7. As described above, the lamphousing 7 can also be formed by molding, making the light emittingdevice 1 at least partially sealed and directly contacted by the lamphousing 7.

According to still another embodiment of the present invention, as shownin FIG. 10, the light emitting device 1 further comprises a reflector 8disposed on the second main surface 22. The reflector 8 can reflect atleast a portion of the light emitted from the second main surface 22 ofthe substrate 2 and increase the light emitted from the first mainsurface 21. This reflector 8 can include, but is not limited to, atleast one metal layer or one Bragg reflector comprising stacked multiplelayers of dielectric thin films with different refractive indices.

As shown in FIG. 11, the light emitting device 1 can further comprisediamond-like carbon (DLC) films 9 disposed optionally on the supportsurface 210 and the second main surface 22 for improving heat conductionand dissipation effects.

As shown in FIGS. 12A to 14D, there are some embodiments of the lightemitting apparatus 11 according to the present invention. According toembodiments of the present invention shown in FIGS. 12A and 12B, thesupport base 5 can further comprise at least one slot or recess to forma socket or adapter 51, and correspondingly the substrate 2 can furthercomprise at least one guide pin or finger connector to connect with theadapter 51 on the support base 5. Wherein the conductors on thesubstrate 2 couple with electrodes of the support base 5 correspondinglythrough the mechanism described above. More particularly, when thesubstrate 2 comprises dual guide pins as shown in FIG. 12B, the polarityof the conductor on one of the guide pins can be different from theother conductor on another guide pin. There is also an embodiment asshown in FIG. 12C that the substrate 2 can be bonded with the supportbase 5 directly, wherein the bonding material used between the substrate2 and the support base 5 can be selected from at least one element ofthe group comprising gold, tin, indium, bismuth, silver, conductivesilicone and epoxy resin. Additionally, the substrate 2 and the topsurface of the support base 5 form a first angle θ₁ wherein the lightingeffect of the light emitting apparatus according to the presentinvention can be changed accordingly.

According to embodiments of the present invention shown in FIGS. 13A to14B, the support base 5 can further comprise at least one support 52coupling with at least one light emitting device 1 of the presentinvention. As shown in FIGS. 13A and 13B, there are at least twosupports 52 spaced from each other wherein the support 52 can beintegrated with the support base 5 or an individual component. Then thesubstrates 2 are coupled to the supports 52 by bonding layers 53,therefore the conductors 23, 24 on the substrate 2 can connectelectrically to the power source accordingly. Furthermore, thesubstrates 2 can be disposed face-to-face as shown in FIG. 13A,back-to-back as shown in FIG. 13B, or face-to-back (not shown) fordifferent lighting effects. Wherein the substrates 2 and the top surfaceof the support base 5 form the first angle θ₁ wherein the lightingeffect of the light emitting apparatus according to the presentinvention can be changed accordingly. Furthermore, the support 52 can beflexible, retractable, or rotatable therefore the lighting effect of thelight emitting apparatus according to the present invention can beadapted to various applications.

As shown in FIGS. 14A to 14D, the light emitting apparatus 11 accordingto the embodiments shown in FIGS. 13A to 13B further comprises a lamphousing 7 and a lamp base 54. Wherein the support base 5 is disposed onthe lamp base 54 and covered by the lamp housing 7, and the lamp housing7 is connected with the lamp base 54. Furthermore, the lamp base 54 canbe integrated with the support base 5. More particularly, the lamp base54 in FIG. 14A can be connected with socket for traditional bulb so thatthe light emitting apparatus of the present invention can directlyreplace the traditional bulb. More particularly, the lamp base 54 inFIG. 14B can be a board like member of the light emitting apparatus 11for different applications like a projector, a decoration wall, or anoperating lamp according to the present invention. More particularly,the light emitting apparatus 11 according to the embodiment shown inFIG. 14C further comprises a wavelength conversion layer 4 disposed onthe lamp housing 7, wherein the wavelength conversion layer 4 isdisposed on the inner side of the lamp housing 7. Therefore, at least aportion of the light emitted from the light emitting device 1 can beconverted to the light of another wavelength before leaving the lamphousing 7. More particularly, the light emitting apparatus 11 accordingto the embodiment shown in FIG. 14D further comprises an additional lamphousing 7, forming a double-layer lamp housing 7 for changing thedecorative patterns and colors conveniently.

The foregoing description is only embodiments of the present invention,not used to limit the scope and range of the present invention. Thoseequivalent changes or modifications made according to the shape,structure, feature, or spirit described in the claims of the presentinvention are included in the appended claims of the present invention.

The invention claimed is:
 1. A light-emitting device comprising: asubstrate comprising a top surface and a bottom surface opposite to thetop surface; and a plurality of LED chips disposed on the top surfaceand configured to generate a top light visible above the top surface anda bottom light visible beneath the bottom surface, each LED chipcomprising a plurality of light-emitting surfaces; wherein the substratehas a thickness greater than 200 μm and comprises aluminum oxide,sapphire, glass, plastic, or rubber, wherein the plurality of LED chipshas an incident light with a wavelength of 420-470 nm, and wherein thetop light and the bottom light have a color temperature difference ofnot greater than 1500K.
 2. The light-emitting device of claim 1, furthercomprising a first conductor and a second conductor located on thesubstrate and electrically connected to the plurality of LED chips. 3.The light-emitting device of claim 2, wherein the each LED chipcomprises a first electrode and a second electrode electricallyconnected to the first conductor and the second conductor respectively.4. The light-emitting device of claim 1, further comprising a wavelengthconversion layer comprising a first portion covering the top surface anda second portion covering the bottom surface.
 5. The light-emittingdevice of claim 4, wherein the first portion of the wavelengthconversion layer contacts the plurality of LED chips.
 6. Thelight-emitting device of claim 4, wherein the first portion and thesecond portion of the wavelength conversion layer comprise one or morekinds of fluorescent powders.
 7. The light-emitting device of claim 1,wherein the substrate is transparent to a light emitted from theplurality of LED chips.
 8. The light-emitting device of claim 1, whereinthe substrate has a transmissivity greater than or equal to 70%.
 9. Alight-emitting apparatus comprising: the light-emitting device of claim1; and a support base coupled to the substrate; wherein the substrate isinclined with respect to the support base by an angle of from 30° to150°.
 10. The light-emitting apparatus of claim 9, further comprising awavelength conversion layer comprising a first portion covering the topsurface and a second portion covering the bottom surface.
 11. Thelight-emitting apparatus of claim 9, wherein the first portion and thesecond portion of the wavelength conversion layer comprise one or morekinds of fluorescent powders.
 12. The light-emitting apparatus of claim9, further comprising a support, wherein the light-emitting device iscoupled to the support base through the support.
 13. The light-emittingapparatus of claim 12, wherein the support base and the support arephysically distinguished from each other.
 14. The light-emittingapparatus of claim 9, wherein the support base has a virtual centeraxis, the plurality of LED chips does not directly face to the virtualcenter axis.
 15. The light-emitting apparatus of claim 14, furthercomprising another light-emitting device of claim 1, which is coupled tothe support base.
 16. The light-emitting apparatus of claim 15, whereinthe plurality of LED chips of the another light-emitting device does notdirectly face to the virtual center axis.
 17. The light-emittingapparatus of claim 9, further comprising a lamp housing covering thelight-emitting device and the support base.
 18. The light-emittingapparatus of claim 17, wherein the lamp housing and the light-emittingdevice are separated from each other by a distance of not equal to zero.19. The light-emitting apparatus of claim 9, wherein the substrate has atransmissivity greater than or equal to 70%.